The invention relates to a method of manufacturing glass bodies, in which the starting material for the glass body is a suspension having a microdispersed solids content which is used to form a porous green body which is subsequently purified and sintered.
The invention further relates to arrangements for carrying out such a method as well as to the use of the glass bodies manufactured by the method in accordance with the invention.
The method mentioned in the opening paragraph is particularly suitable for the manufacture of preforms for optical waveguides.
For the manufacture of very pure quartz-glass bodies, particularly preforms for optical waveguides, methods are known in which a porous green body is manufactured from micro-dispersed SiO.sub.2 glass particles, after which the said green body is first purified in, for example, a chlorine-containing atmosphere at temperatures ranging from 600.degree. to 900.degree. C. Next, the green body is sintered at a temperature of approximately 1500.degree. C. to form compact and transparent glass; the sintering temperature depends upon the size of the SiO.sub.2 particles and the homogeneity of the green body.
Processing of micro-dispersed quartz-glass particles involves a substantial investment in equipment (preforms for the manufacture of a green body which is easy to manipulate and presses to compact this green body) in order to obtain a green body having a density which is so high as to enable an efficient sintering process, i.e. sintering at temperatures .ltoreq.1550.degree. C. to form a glass body which is free from bubbles and reams. Such a method for the manufacture of a preform for optical waveguides is known from, for example, DE-PS No. 32 40 355.
For the manufacture of green bodies having a sufficiently high density, an alternative method may be used in which micro-dispersed SiO.sub.2 suspensions are deformed into a green body. DE-OS No. 29 25 309 describes a method in which a SiO.sub.2 suspension is sprayed in or on a carrier tube. A disadvantage of this method is that high demands are made on the spraying arrangement as regards the necessity of an even distribution of the SiO.sub.2 suspension, and that purification of the green body in a hot gaseous atmosphere which reacts with the impurities is impossible because the carrier tube is not porous.